Method and apparatus for continuous flow injection extraction analysis

ABSTRACT

A method and apparatus for a continuous flow injection batch extraction  aysis system is disclosed employing extraction of a component of a first liquid into a second liquid which is a solvent for a component of the first liquid, and is immiscible with the first liquid, and for separating the first liquid from the second liquid subsequent to extraction of the component of the first liquid.

CONTRACTUAL ORIGIN OF THE INVENTION

The U.S. Government has rights in this invention pursuant to ContractNo. DE-AC07-84ID12435 between the U.S. Department of Energy andWestinghouse Electric Company.

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for continuousflow injection extraction analysis employing flow injection solventextraction.

Continuous flow analytical systems in which there is provided acontinuous unobstructed carrier stream into which discrete volumes ofsample solutions are injected for reaction with the carrier stream areknown and described in U.S. Pat. Nos. 4,013,413 and 4,022,575. However,the systems described therein for solvent extraction analysis havedrawbacks in that the segmenters and phase separators described therein,typically need frequent maintenance and adjustment for continuingreliable results. Thus the need for such adjustments has been anobstacle in the development of a system capable of continuous, fullyautomated analytical procedures involving extraction of a liquid samplewith an immiscible solvent. The present invention overcomes theseproblems.

SUMMARY OF THE INVENTION

An object of the present invention is to overcome the deficiencies offlow injection analysis systems known in the prior art. The system ofthe present invention provides superior mixing of phases which favorsmore efficient extraction per unit time, and also provides trouble-freephase separation prior to the final detection of the extracted analytein the lighter phase.

The analytical system according to the invention comprises, an apparatusand method for extracting an analyte component of a first liquid phaseinto a second liquid phase which is a solvent for the analyte componentof the first liquid phase, and which is immiscible with the first liquidphase. The second liquid phase is separated from the first liquid phasesubsequent to extraction of the analyte component. The apparatus forcarrying out the extraction includes means for supplying a first portionof the first liquid phase into a mixing device at a substantiallyconstant flow rate while the apparatus is in operation. Means are alsoprovided for injecting the second liquid phase into the first portion ofthe first liquid phase. Then, a second portion of the first liquid phasecontaining the analyte component is injected into the first portion ofthe first liquid phase. The mixing device comprises an upper portion anda lower portion. The lower portion includes a mixing chamber having anopening through which the chamber is filled with the first and secondliquids and means for vigorously mixing the two liquid phases. Theanalyte component of the first liquid phase is extracted into the secondliquid phase during the vigorous mixing thereof. The upper portion ofthe apparatus includes a separator for aiding the natural separation ofthe second liquid phase from the first liquid phase subsequent to theextraction, and an outlet through which the second liquid phase isremoved subsequent to separation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a preferred embodiment of thesystem and apparatus of the present invention including a crosssectional view of the mixing device associated therewith.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In a preferred embodiment as shown in FIG. 1, a continuous injectionbatch extraction analysis system 1 is provided which comprises a mixingdevice 10 and a flow system 12. The flow system 12 comprises a supplysource such as a reservoir 14 for containment of a reagent or carrierliquid 16. A supply conduit 18 extends from the outlet 20 of thereservoir 14 to inlet 21 of two position rotary valve 23. Outlet 25 ofrotary valve 23 extends to inlet 22 of supply pump 24 through conduit 18thereby placing the reservoir 14 in fluid communication therewith. Thesupply conduit 18 further extends from the outlet 26 of the supply pump24 to the inlet 28 of the mixing device 10.

The first 30 and second 32 valve injectors are placed in series betweenthe supply pump 24 and the mixing chamber 10. The supply conduit 18 isconnected to the first valve injector 30 through the inlet 34. Thesupply conduit 18 then extends from the outlet 36 of the first valveinjector 30 to the inlet 38 of the second valve injector 32. The supplyconduit 18 is then connected from the outlet 40 of the second valveinjector 32 to the inlet 28 of the mixing device 10. A reservoir 42contains a low density, water-immiscible, solvent/extractant liquid 44for supply to the first valve injector 30 through the second inlet port49. A second reservoir 46 contains an aqueous sample liquid 48 forsupply to the second valve injector 32 through the second inlet port 50.

The mixing device 10 is comprised of two sections, an upper block 72 andlower block 74, preferably constructed of Teflon® material. Teflon®(polytetrafluoroethylene) was found to be the most suitable material forcarrying out the purposes of the present invention due to its low slipresistance and its non-reactive properties with respect to the liquidsutilized. Upper block 72 comprises a phase separator 52 and lower block74 comprises mixing chamber 54. At the bottom 56 of the mixing chamber54, is an inlet 58. A plug 60 interconnects the inlet 58 with the supplyconduit 18 of the flow system 12 to allow the flow of materials into thebottom 56 of the mixing chamber 54.

The side walls 62 of the mixing chamber 54 are machined or otherwisearranged with a plurality of flutes or recesses 64 to aid in thethorough mixing of the liquid materials 16, 44 and 48. A magneticstirring bar 66 is located proximate to the bottom 56 of the mixingchamber 54. When rotated by electric coils about the mixing chamber 54,the magnetic stirring bar 66 rotates in a rapid fashion as the liquids16, 44 and 48 enter the mixing chamber 54, thereby vigorously mixingsame.

The phase separator 52 of the mixing device 10 is substantially conicalin shape having upwardly angled walls 68, which are pointed upwardlytoward the outlet 70 of the mixing device 10. In a preferred embodiment,the phase separator 52 and the mixing chamber 54 of the mixing device 10are sealed together with bolts 76 and 78.

To perform an extraction, the supply pump 24 is activated, therebypumping a carrier liquid 16 from the reservoir 14 into the mixingchamber 54 via the supply conduit 18. The bypasses 80 and 82 associatedwith the first 30 and second 32 valve injectors, respectively, allow thecarrier liquid 16 to be pumped into the mixing chamber 54 while valveinjector 30 is filled with liquid 48 and valve injector 32 is filledwith liquid 44.

The first valve injector 30 and second valve injector 32 each includes afirst plug chamber 84 and a second 86 plug chamber, respectively, forcontainment of a small portion of the liquids 44 and 48 from thereservoirs 42 and 46, respectively. When the first valve injector 30 isactivated, the first plug chamber 84 is electronically rotated such thatport A is in line with inlet 34 and port B is in line with outlet 36.Similarly, when the second valve injector 32 is activated, the secondplug chamber 86 is electronically rotated such that port C is in linewith inlet 38 and port D is in line with outlet 40. As such, when thefirst 30 and second 32 valve injectors are activated, the carrier liquid16 is pumped into the mixing chamber 10 through the first valve injector30 and the second valve injector 32, thereby carrying plugs ofsolvent/extractant liquid 44 from the reservoir 42 and the aqueoussample liquid 48 from the reservoir 46 into the mixing chamber 10.

At this point in the process, the combined volume of the carrier liquid16, the solvent/extractant liquid 44 and the aqueous sample liquid 48 isless than the volume of mixing chamber 54. The magnetic stir bar 66 isthen activated, such that it rotates at a very high speed, therebyvigorously mixing the combined volumes of the respective liquids 16, 44and 48. Simultaneous therewith, the first valve injector 30 and secondvalve injector 32 are deactivated. The supply pump 24 continues to pumpthe carrier liquid 16 into the mixing chamber 54 of the mixing device 10through the inlet 58. Because the first valve injector 30 and the secondvalve injector 32 are deactivated, the carrier liquid 16 is pumpedaround the first 30 and second 32 valve injectors through the bypasses80 and 82, respectively.

Since both the carrier liquid 16 and sample liquid 48 are aqueous, thetwo liquids 16 and 48 mix completely upon initial contact. However,solvent/extractant liquid 44 is water-immiscible, and therefore does notmix with carrier liquid 16 and sample liquid 48 upon initial contact.Therefore, there are essentially two immiscible liquids within mixingdevice 10 comprising two liquid phases. The first liquid is in anaqueous phase and comprises the carrier liquid 16 and the sample liquid48. The second liquid is in an organic non-aqueous phase and comprisessolvent/extractant liquid 44.

The stirring bar 66 continues to rotate at a high speed as the first andsecond immiscible liquids are violently mixed in the mixing chamber 54of the mixing device 10. The flutes 64 which are cut into the side wall62 of the mixing chamber 54, assist in breaking up laminar layered flowof the first and second immiscible liquids, and causing the efficientmixing necessary for efficient extraction. As the vigorous mixingcontinues, the analyte in sample liquid 48 which comprises part of thefirst liquid phase, is chemically extracted into the solvent/extractantliquid 44 which comprises the second liquid phase.

The supply pump 24 continues to pump carrier liquid 16 into the mixingchamber 54 of the mixing device 10, thereby eventually raising thecombined volume of liquids 16, 44 and 48, in phase separator 52 ofmixing device 10. As the level of liquids 16, 44 and 48 increases, themixing becomes far less efficient and phase separation starts to occurin the conical, upwardly angled walls 68 of the phase separator 52 inmixing device 10. As phase separation begins in the phase separator 52,the solvent/extractant liquid 44 with the analyte moiety of sampleliquid 48 extracted therein, is in an organic non-aqueous phase, and isof a lower density than the carrier liquid 16, and therefore rises tothe top.

The continuous filling of the mixing chamber 54 with carrier liquid 16pushes the organic non-aqueous phase of the solvent/extractant liquid 44with the portion of sample liquid 48 extracted therein out of the phaseseparator 52. At this point, phase separation is complete. Thesolvent/extractant liquid 44 having a portion of the sample liquid 48extracted therein, then exits the mixing device 10 through tubing 88 andis then vented to a post extraction reaction system or detector (notshown).

A conductivity sensor 90 is located at the top 92 of the mixing chamber10, and is activated to sense when the solvent/extractant liquid 44,(having the portion of sample liquid 48 extracted therein), iscompletely pumped out of the mixing device 10. This is done by sensingthe conductivity of the carrier liquid 16. Because the carrier liquid 16is of a higher density and remains beneath the organic non-aqueous phaseof solvent/extractant liquid 44, when the conductivity sensor 90 sensesthe known conductivity of the carrier liquid 16, it is also known thatsolvent/extractant liquid 44 is completely out of mixing device 10. Whenthe conductivity sensor 90 senses the carrier liquid 16, the system isdeactivated, thereby prohibiting the carrier liquid 16 fromcontaminating the organic nonaqueous phase of the solvent/extractantliquid 44.

When the above described extraction cycle is completed, the mixingdevice 10 is then flushed clean by switching the two way rotary valve 23to connect conduit 18 through outlets 21 and 25 to conduit 93 throughoutlet 27. Conduit 93 is connected to flush loop 95 through which wateror some other suitable flushing liquid 97 continuously flows to wastedrain 99. Pump 24 is then reversed to pump all of the contents of themixing chamber 54 into flush loop 95. If it is deemed desirable to flushthe system, pump 24 is reversed again to fill mixing chamber 54 and allintermediate conduits with flush liquid 97 after which pump 54 isreversed again to exhaust the rinse/flush liquid back into flush loop95. A new extraction cycle may be initiated by switching the two wayrotary valve 23 to connect conduit 18 through outlet 25 to conduit 18through 20 and reversing pump 24.

The entire process described above including timing means and activationand deactivation of the various components, may be operated by asequence programmer or programmable controller or similar automaticcontrolling apparatus.

In the preferred embodiments, the batch extraction analysis system 1 ofthe present invention is used to extract uranium from an aluminumnitrate salting solution into hexone. In such an embodiment, the carrierliquid 16 comprises aluminum nitrate, the solvent/extractant liquid 44comprises hexone or a similar hydrocarbon solvent, and the aqueoussample liquid 48 comprises a uranium solution. The impure uranium samplesolution combines immediately with the aluminum nitrate, both beingaqueous, to form a first liquid, but they do not immediately mix withthe non-aqueous hexone, which represents the second liquid. As themagnetic stirring bar 66 begins to vigorously mix the two liquids,molecules of nitrate from the aluminum nitrate combine and attach tomolecules of pure uranium from the impure uranium solution, and thecombined molecules are then enabled to be chemically extracted into thehexone. Nitrate by itself is not extractable into hexone and uranium byitself is not extractable into hexone. However, when the nitrate anduranium molecules combine, this combination allows for extraction intothe non-aqueous hexone. The impurities in the uranium solution remain inthe aqueous phase as the pure uranium is extracted into the non-aqueousphase. As the extraction and phase separation is complete, the hexone,having pure uranium therein, is pumped from the mixing chamber 10 into apost extraction reaction system.

The batch extraction analysis system 1 of the present invention has alsobeen tested with satisfaction using thiocyanate as the aqueous carrierliquid, hexone or a similar hydrocarbon solvent as thesolvent/extractant liquid and cobalt as the sample liquid.

It is anticipated that other useful extractions may be accomplished withthe batch extraction analysis system of the present invention. Examplesof such include analytical applications in which the heavier phaseextracts the analyte component from a lighter phase (requiring theextracted analyte to be collected from the bottom of the mixingchamber), and in which both liquid phases are continuously feeding intothe mixing chamber with subsequent collection of the lighter phase fromthe top and the heavier phase from the bottom. In the continuous mode,this system can be used in non-analytical application to removecontained waste from a solvent for eventual recycle of the originalsolvent.

The foregoing description and drawings merely explain and illustrate theinvention, and the invention is not limited thereto, except insofar asthose who have the disclosure before them are able to make modificationsand variations therein without departing from the scope of theinvention.

The embodiment of the invention in which an exclusive property orprivilege is claimed is defined as follows:
 1. A method for extractinguranium from an aluminum nitrate salting solution comprising the stepsof:pumping a carrier stream of aluminum nitrate through first and secondsampling injection valves and into a mixing device; injecting an aliquotof low-density, water-immiscible, hexone as a solvent-extractant fromsaid first sampling injection valve into the first portion of saidcarrier stream; subsequently injecting an aliquot of impure uraniumsolution from said second sampling injection valve into said carrierstream, wherein said hexone and said impure uranium solutions areconveyed into said mixing device by said carrier stream; vigorouslymixing said hexone with said uranium and aluminum nitrate solution inthe lower portion of said mixing device with a magnetic stirring bar;continuously and gradually filling said mixing device with said aluminumnitrate during said vigorous mixing; chemically extracting molecules ofpure uranium combined with molecules of nitrate into said hexone duringsaid vigorous mixing; separating said hexone having pure uranium thereinfrom said aluminum nitrate having impurities therein by allowing saidhexone to float to the top of the upper portion of said mixing device;and forcing said separated hexone with said pure uranium therein out ofthe top of said mixing device by said continuous filling of said mixingdevice with said aluminum nitrate.
 2. The method as described in claim1, wherein said mixing device comprises an upper portion and a lowerportion wherein said lower portion comprises a cylindrical mixingchamber having an inlet and magnetic stirbar proximate the bottomthereof and having a plurality of grooves cut into the interior wallsthereof for aiding said mixing and wherein said upper portion comprisesa substantially conical separator having upwardly angled walls and anoutlet at the top thereof.
 3. The method of claim 1, wherein saiduranium changes from an initially impure aqueous phase into a pureorganic non-aqueous phase.
 4. The method of claim 1, wherein said methodfurther comprises the steps of:sensing the conductivity of said aluminumnitrate having impurities therein as it exits said mixing device; andceasing the operation of said extraction upon said sensing, therebyinhibiting the contamination of said pure uranium which first exits saidmixing device.
 5. A method for extracting a component of a first aqueousliquid into a second non-aqueous liquid comprising the stepsof:continuously flowing a stream of said first aqueous liquid into amixing device; introducing said second non-aqueous liquid comprising anon-aqueous solvent-extractant into said stream of said first aqueousliquid; introducing an aqueous sample into said stream; flowing saidnon-aqueous solvent extractant and said aqueous sample into said mixingdevice along with said first aqueous liquid; combining said firstaqueous liquid with said aqueous sample, thereby forming an aqueousmixture; vigorously mixing said aqueous mixture with said secondnon-aqueous liquid in said mixing device while continuously filling saidmixing device with said first aqueous liquid; chemically extracting acomponent of said first aqueous liquid into said second non-aqueousliquid during said vigorous mixing; separating said second non-aqueousliquid from said first aqueous liquid by allowing said secondnon-aqueous liquid to rise to the top of said mixing device; forcingsaid second non-aqueous liquid out the top of said mixing device by saidcontinuous filling of said mixing device with said first aqueous liquid;and flushing said mixing device by pumping said liquids from said mixingchamber to a drain.
 6. The method of claim 5, wherein said stream ofaqueous carrier liquid is acid-deficient aluminum nitrate, said aqueousmulti-component sample is impure uranium solution and said second liquidis hexone.
 7. The method of claim 5, wherein said method is controlledby sequence timing means.
 8. The method of claim 5, wherein said secondliquid is of a lighter density than said aqueous carrier liquid.
 9. Themethod of claim 5, wherein said method further comprises sensing theconductivity of said first liquid as it exits said mixing device andceasing the operation of said extraction upon said sensing, therebyinhibiting the contamination of said second liquid which first exitssaid mixing device.
 10. An apparatus for extracting a component of afirst liquid into a second liquid which is a solvent for a component ofsaid first liquid and is immiscible with said first liquid, and forseparating said second liquid from said first liquid subsequent to saidextraction, said apparatus comprising:a mixing device having an upperportion and a lower portion; means for supplying a first portion of saidfirst liquid into said mixing device at a substantially constant flowrate while said apparatus is in operation; means for injecting saidsecond liquid into said first portion of said first liquid wherein saidsecond liquid is carried into said mixing device; means for injecting asecond portion of said first liquid into said first portion of saidfirst liquid wherein said second portion is carried into said mixingdevice; and said lower portion of said mixing device comprising a mixingchamber having an inlet through which said mixing chamber is filled withsaid first and second liquids and mixing means for vigorously mixingsaid first and second liquids, whereby a component of said first liquidis extracted into said second liquid during said vigorous mixing; andwherein said upper portion of said mixing device comprises a separatorfor aiding the natural separation of said second liquid from said firstliquid subsequent to said extraction, and an outlet through which saidsecond liquid is removed subsequent to said separation.
 11. Theapparatus of claim 10, wherein said means for supplying a first portioncomprises a pump which pumps said first portion of said first liquidfrom an external source through said inlet into said lower portion ofsaid mixing device, remove liquids from mixing device, and fills andempties mixing device with said flushing solution.
 12. The apparatus ofclaim 10, wherein said means for injecting said second liquid and saidmeans for injecting a second portion of said first liquid compriseindividual injection valves respectively.
 13. The apparatus of claim 10,wherein said lower portion of said mixing device is substantiallycylindrical, and has a plurality of grooves cut into the interior wallsthereof so as to aid in the thorough mixing of said first and secondliquids.
 14. The apparatus of claim 10, wherein said upper portion ofsaid mixing device is substantially conical in shape and has upwardlytapered walls for aiding the separation of said first and secondliquids.
 15. The apparatus of claim 10, wherein said mixing device isconstructed of polytetrafluoroethylene.
 16. The apparatus of claim 10,wherein said apparatus further comprises a conductivity sensor forsensing when said first liquid begins to exit said mixing device. 17.The apparatus of claim 16, wherein said sensing ceases the operation ofsaid apparatus so that said first liquid is inhibited from contaminatingsaid second liquid subsequent to said extraction.
 18. The apparatus ofclaim 10, wherein said mixing means comprises a magnetic stirbar.